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In TWIP #33, Dr Despommier said that certain parasites do not need receptors to enter cells, while Dr Racaniello then said that all viruses require a receptor for entry. I might be wrong but don't certain paramyxoviruses like Respiratory Syncytial Viruses enter the host cell by mere membrane fusion? I hope I'm not missing the point here, but i remember being taught in my undergraduate course that there are a certain class of viruses that don't need a receptor at all.

Thanks

Steve writes:

I first read of the Red Queen's Hypothesis in Parasite Rex by Carl Zimmer, which list Dr. Despommier in the acknowledgements. Recently there was an story in The Wall Street Journal: "Why Sex? To Keep Parasites at Bay, of Course" by Matt Ridley. I believe it would be very helpful to hear your thoughts on the Red Queen's Hypothesis.

Thanks, we appreciate all of your great podcasts.

Scott writes:

Vincent & Dickson,

I listened with great interest this afternoon to the TWIP story on malaria vaccine (via Science360 - I am not an academic, but a true science junkie). My keen interest is due to the fact that I lived in Nigeria for some time and suffered from P. falciparum infection seven times before I was finally able to build enough immunity to not suffer mightily. No cerebral, thank goodness! But it left me with a passion for watching developments in the study of the parasite and the science of malaria control.

In listening to the part on the TWIP podcast about the locus of injection site being critical to efficacy for this possible vaccine candidate, a thought occurred to me: Since mosquitos are so adept at finding blood vessels from which to suck their bloodmeal, why not create a genetically modified mosquito that would produce the candidate vaccine protein in its saliva, so that when it inserts its proboscis into the blood capillary, the host gets a tiny injection of the protein at the same time. While I do expect that not a single mosquito bite would produce immunity, of course, the many thousands that one receives over time, might do the job, and would maintain it over time, as "booster shots" would be received daily. Since this vaccine seems to be efficacious against all the strains it has been tried against, it would suggest that the parasite's docking protein is highly conserved in evolution, making the evolution of resistance much less likely.

If the same genetic sequence were also used to invoke immunity to Plasmodium by the mosquito itself, it would give the mosquitos an evolutionary advantage in the environment, in that there is also a cost to the mosquito as well in carrying the parasite. This would ensure that the genetic modification would become dominant in the mosquito population over time. It would also provide a double-pronged attack on the parasite - both at the mosquito and human blood stages of the parasite's life cycle would be suppressed.

While I recognize that there are surely some formidable barriers in the way of creating such a system and deploying it in the field, my thought is that it might have enough promise to be worth looking into.

Warmest regards from (so far) malaria-free Cartago, Costa Rica,

Trudy writes:

Listening to you in Podcast #6 on tapeworms. You are making me laugh. I live in Florida. Not everyone is retired in Florida. Not even people who live in South Florida are all retired.FYI Whole Foods does list the country of origin of the animal proteins sold in their stores.With my background in Public Health epidemiology and communicable disease clinic (STD clinician...TB outreach), I have never seen a tapeworm in a specimen since moving to Florida. I had seen on in the teaching hospital I worked at in Grand Rapids, Michigan in a specimen from an immigrant. Now I said not everyone in Florida is retired and they are not...but I am retired (early).

Cattle ranches are not just in the panhandle either...many of these ranches are all over the state. Florida is a big state, we have a lot of open land used for all types of agricultural purposes. While there are beef cattle grown in Florida, many more farms/ranches are devoted to dairy production.

I am a nurse, an artist and a Florida Master Naturalist....science, microbiology and infectious diseases continue to be of tremendous interest to me.

Charlotte writes:

In TWIP 33 you asked which protozoa should be discusesed in future episodes. If you discuss Acanthamoeba as a "Trojan Horse" you can correct errors made on two episodes of TWIM regarding Legionella as endosymbionts of Acanthamoeba.

I think listeners would find comparisons of Acanthamoeba, Neglaria and Hartmonella (in terms of pathogenesis and as bacterial reservoirs) interesting.

Thank you for the podcasts, without which I would never sleep.

Charlotte

P.S. The "Trojan Horse" term was coined by Barker & Brown, but everybody uses it now.